1. Field of the Invention
The present invention relates to a sound field generator and a method of generating a sound field using the same. More particularly, the present invention relates to a sound field generator and a method of generating a sound field using the same, which can apply a filter in consideration of a masking effect in a time domain to a room impulse response, remove inaudible data depending on a frequency in a signal obtained by multiplying the room impulse response by an input signal in a frequency domain, and remove signal blocks having a lower level than a level of background noise blocks among output signal blocks to considerably reduce computational complexity required for performing a convolution, making it possible to generate an accurate sound field by minimizing sound quality distortion while implementing a real-time sound field generating system.
2. Description of the Related Art
A sounder generating a sound field effect in a special space generally performs a convolution operation of a room impulse response (hereinafter, referred to as “RIR”) based on a finite impulse response (hereinafter, referred to as “FIR”) on a sound signal, when applying the sound field. Comparing to a method based on an infinite impulse response, this method performs a direct convolution on an input signal and the impulse response signal, making it possible to reduce sound quality distortion and obtain the sound field effect approximating the actual sound field effect. However, since this method has enormous computational complexity in respects to a length of the RIR in a specific sound space, it cannot be applied to an apparatus requiring real-time processing.
A block convolution algorithm has been proposed to reduce a delay of computing time and linear convolution operation in the FIR based sound field generating apparatus. The block convolution algorithm divides the input signal and the impulse response signal into several blocks to overcome the above-described problem caused when the RIR is long. The block convolution algorithm can be applied to apparatuses requiring the real-time convolution operation, such as a sound 3D rendering system and a real-time sound player.
FIG. 1 is a block diagram of a block convolution algorithm used in a general FIR based sound field generating apparatus.
The input signal is divided into several input signal blocks 10 and the RIR signal is also divided into several RIR blocks 30. Δt this time, each signal block has the same length. Each input signal block 10 is transformed into a frequency domain by a fast Fourier transform (FFT) 20 and each RIR block 30 is also transformed into a frequency domain by the fast Fourier transform 40. The input signal block and the RIR block transformed into the frequency domain are multiplied in a multiplier 50, which are then output to each signal block 60 and are transformed into a time domain by an inverse fast Fourier transform (IFFT) 70. Each block transformed into the time domain is integrated into one signal so that a sound signal 80 including the sound field effect is produced.
Such a general FIR based sound field generating apparatus repeats the computation at a number of block units several times, as can be seen from FIG. 1, but it does not perform filtering in consideration of human auditory characteristic in each computational step to lead to a problem of enormous computational complexity. Since the general FIR based sound field generating apparatus has enormous computational complexity, its processing speed is slow. Therefore, in order to supplement it, the general FIR based sound field generating apparatus requires an expensive processor and a large-capacity memory, which causes an increase in manufacturing cost.